Exelon Generation’s 1,246-MW Limerick-1 nuclear unit in Limerick, Pennsylvania, has begun its coast to a refueling and maintenance outage.

Company spokeswoman Emily Ryan said in an email Friday that the reactor was “currently at 99% power as part of the unit’s end-of-cycle coastdown. For competitive reasons, Exelon Generation does not disclose outage schedules for its generating units.”

US nuclear power units typically reduce their output gradually before shutting for refueling. This “coastdown” period lasts from several days to several weeks.

The average duration of refueling outages at US nuclear units in 2016 was 35.6 days, according to S&P Global Platts data.